ICD-10 Code D37.3 – Neoplasm of uncertain behavior of appendix (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D37.3 – Neoplasm of uncertain behavior of appendix
What it is
D37.3 identifies a tumor of the appendix whose behavior cannot be determined from the available information. Use it when pathology or documentation shows uncertain malignant potential, and the record does not confirm a benign or malignant diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Patients may have an appendiceal mass, incidental imaging finding, or pathology report describing uncertain behavior, but the diagnosis depends on the documented tissue interpretation, not symptoms alone.
When to use this code
Use D37.3 when the provider documents a neoplasm of the appendix with uncertain behavior or borderline malignant potential. It is also appropriate when pathology confirms an appendiceal lesion but does not classify it as benign or malignant. Check documentation if the site is described differently.
Do not use for
Do not use this code for clearly benign appendiceal lesions or for confirmed malignant neoplasms of the appendix. If the record describes appendicitis, mucocele, or another non-neoplastic condition, choose the more specific diagnosis instead.
Coding tip
Code the documented behavior and site exactly as stated; if the appendix is not explicitly named, verify the anatomic source before assigning D37.3.